Magneto



l Feb. 27, 1934.

MAGNETO Filed Aug. 29, 1932 IN VEN TOR.

BY Z) f ATTORNEY.

c. F. REIS 1,948,828

Patented Feb. 27, 1934 vlaliriazlv'r ori-ics MAGNEro Curt F. Reis,Beloit, Wis., assigner to Fairbanks, Morse & Co., Chicago, Ill., acorporation of Illinois Application August 29, 1932. Serial No. 630,87540mm.' (el. 1v1-252)' This invention relates to improvements inmagnetos, and more particularly to improvements in rotors of magnetos ofthe type employing rotating permanent magnets.

In certain prior types of magnet rotors, it is usual to employ a mass ofcast non-magnetic metal, such as brass, for the rotor shaft, and forintimately uniting the laminated pole shoes. Such structures areobjectionable, in that a cast l0 shaft is comparatively low in tensilestrength, and is rather expensive for shafting material.

In magnetos of this type, it is desirable to employ permanent magnetsformed of cobalt steel or other materials having high magnetic re- 16tentivity. Such materials have not been widely used in magnetos becauseof the diiliculty experienced in machining, and in securing the polepieces to the rotor. In prior types of rotor constructions it is usualto employ screws or other like fastening means for securing thepermanent magnets and the various other parts to the rotor shaft. Suchconstructions are objectionable in that the screws become loose andineffective.

An object of the present invention is to provide an improved rotor formagnetos of the type above noted, which includes a rotor shaft formed ofsteel or other similar material, and a mass of diecast aluminum or zincalloy for intimately uniting the laminated pole shoes to the shaft. Bythis provision, a shaft of substantial strength and rigidity is employedin the rotor assembly.

A further object is to provide an improved con'- struction of rotors, ofmagnetos of the rotating field type which includes a mass of die-castnonmagnetic metal for Asecuring the laminated pole ,shoes and magneticbridging member to the rotor shaft, and means for removably securing thepole pieces into` intimate contact with the pole shoes and bridgingmember.

A still further object is to provide an improved rotor for magnetos ofthe rotating field type in which the laminated pole shoes and themagnetic pole bridging member are intimately united tc the rotor shaftby means of a mass of die-cast non-magnetic metal, and in which the polepieces are removably assembled and more firmly secured to the die castmass, than is possible through the use of screws, bolts. nuts or thelike.

An additional object is to provide an improved rotor for magnetos of therotating field type, which is rigid and durable in construction, and iscomposed of but a few simple and easily assembled parts, andwhichresults in a substan- 55 tial reduction of production costs, throughmini'- mization of machining operations on the permanent magnets.

Further objects and advantages will appear from the following detaileddescription of parts, and the accompanying drawing of a singlepre- 00ferred embodiment, and in which:

Fig. 1 is a longitudinal section of a preferred form of rotor formagnetos of the rotating field type, the section being taken along line1--1 of Fig. 3; Fig. 2 is a section taken along line 2--2 in 65 Fig. 1;Fig. 3 is a section taken along line 3-3 in Fig. l; Fig. 4 is a sectiontaken aiong line 4 4. in Fig. 1; Fig. 5 is a fragmentary section takenalong line 5--5 in Fig. 3; Fig. 6 is a reduced section taken along line2--2 in Fig. 1, and show 70 ing a modified pole shoe construction; andFig. 7 is a section, substantially reduced in' size, taken' along line4-4 in Fig. 1 and showing a modified form of magnet bridging member tobe employed lin connection with the pole shoe construction 7l shown inFig..6.

Referring by 'numerals to the drawing, the numeral 10 designates,generally, a preferred form of rotor for magnetos of the 'rotating fieldtype, and which includes a rotor shaft 11 formed, 00 by preference, ofmild steel or other similar shafting material of substantial strengthand rigidity.

A plurality of pole pieces or permanent magnets 12, are, by preference,arranged in spaced rela.- tion and substantially parallel to each other,Il and to the longitudinal axis of the shaft. These pole pieces are, bypreference, formed of cobalt steel or other material possessing highmagnetic retentivity, and are formed, by preference, circular in crosssection to facilitate machining oper- 00 ations. In the preferredexample shown, the rotor 10 .includes four such pole pieces, although itwill be understood that the number may be varied, depending upon thetype and number of poles of the magneto to be constructed.

Referring more particularly to Figs. 2 and 4, wherein the parts of therotor are arranged for a two pole machine, a pair of bridging members 13of stamped soft iron or steel, are Adisposed near one end of the rotorand each in contact with the end portions of a pair of the pole pieces12 of opposed polarity. Each bridging member provides a flux pathbetween the paired pole pieces of opposite polarity, to provide astructure which is, in effect, a U shaped permanent magnet. By thisarrangement there are provided two distinct magnetic circuits within therotor, .where a two pole machine is desired. Each bridging member 13 isprovided' with an intermediate semi-circular recessed portion 14. Byreason of this construcllq tion, there results an annular space 15,which separates the shaft 11 from the opposed recessed inner margins ofthe members 13. Pole shoes 16 are provided, and consist of stacks ofsoft iron laminations, each of partly sector shape, which are arranged,respectively, on the free ends of the pole pieces 12, each 'pole shoeconnecting the pole pieces of like polarity. Each lamination is, bypreference, provided with a pair of apertures 17 which are slotted asindicated at 18, the pole pieces extending through these apertures. Itwill be readily seen that the pole shoes 16 only partially encircle thepaired pole pieces, because of the slotted portion 18 of thelaminations.

In assembling the rotor, the laminated pole shoes, bridging members 13,together with the rotor shaft. are suitably positioned in a die-castingmold. The mold, prior to casting, is provided with cores correspondingin size and shape with, and so as to result in, openings 20. In similarmanner, paired tapered slots 21 are provided by suitable cores in thedie-casting mold. A mass of non-magnetic metal 22, such as a suitablealuminum or zinc alloy, is then poured into the mold for intimatelyuniting to thel shaft, the assembled laminations for the pole shoes, andthe bridging members. After the die-casting process, the resultingrigid, integral structure is removed from the mold, the corescorresponding to openings 20 and slots 21, removed from the casting, andthe pole pieces 12 are inserted through the pole shoe apertures 17 andthe cored openings 20. Each pole piece is provided with a slotted ornotched portion 23, which is arranged to be aligned with the slots 21previously cored in the mass of metal 22. These notched portions are sodisposed on each pole piece as to be aligned with the adjacent orcorresponding slot 21 when the pole piece is in contact with thebridging piece 13. A tapered wedge orpin 24 is then driven or pressedinto each slot to secure the pole pieces to the mass of cast metal, andto prevent any appreciable endwise or rotary movement of the polepieces. relative to the cast portions of the structure. These wedge pinsmay also be so constructed that, upon insertion, they serve to urge theends of the pole pieces into intimate coritact with the soft ironbridging members 13, to insure good magnetic contact between thebridging members and pole pieces. The wedge pins may be formed of asuitable non-magnetic material, and as illustrated, each pin serves tohold a pair of the pole pieces of opposed polarity, in place in theassembly. The rotor is now completely assembled, and ready for use in amagneto, and it will be apparent that by the above arrangement allscrews or threaded fastening means for assembling the rotor, areeliminated, a much easier and more secure assembly expedient beingprovided by the wedge pins.

In Figs. 6 and 7 certain o'f the rotor parts are shown as arranged for afour pole machine. vIn this modification, a plate 25 of stamped softiron or steel is disposed near one end of the pole pieces 12, in placeof the bridging members 13 employed in the above described two polemachine. The plate 25 provides a flux path common to all the polepieces. A central circular aperture 26 is punched in the plate 25,which, when the plate is assembled in the rotor, causes the plate to beseparated from the shaft 11 by an annular web 27 of the casting metal.Pole shoes 28 consisting" of stacks of soft iron laminations, arearranged on the free ends of each pole piece, to form four separate anddistinct poles. Each lamination is provided with a slotted aperture 29similar to that shown in Fig. 2. It will be readily seen that thevarious parts are assembled in the same manner as described for the two'pole machine.

In either construction above described, it will be seen that the mass ofnon-magnetic metal secures the various parts of the rotor to the shaft,and that a web of non-magnetic metal, magnetically insulates thebridging members 13 or the plate 25 from the shaft. The tapered slots 2lare, by preference, formed with a tapered wall portion 30 and anopposite, straight wall portion 31. By this provision, the slots in thepole pieces may be ground without taper, to facilitate machining andassembling. It will be readily seen that the pole pieces 12 may beremoved for remagnetizing purposes, simply by withdrawing the wedge pins24. After remagnetization, the poles may be reinserted and again securedin place by the pins 24. The use of these wedge pins eliminatesexpensive and difdcult machining operations on the hard steel magnets.'I'he only machining operation, viz., that of grinding the straightslots 21, is simple and inexpensive, as compared to the machiningnecessary with prior types of rotors. It will also be readily seen thatall the parts of the rotor, with the execption of the tapered pins 24and pole pieces 12, are metallically united into a rigid unitarystructure in the diecasting process.

The rotor shaft 11 is, by reference, provided with a knurled portion 32to insure good interengaging coherence between the mass of cast metal 22and the shaft. This knurled portion prevents any relative movement, dueto an improved bond between the cast metal 22 and the shaft. It will beapparent that the present improved rotor is neat and compactinconstruction, and forms practically a rigid, solid, rotating mass. Itwill, of course, be understood that my preference is not to die-cast thepole pieces in place. since the heat developed during the die-castingprocess would anneal the pole pieces resulting in a loss in magneticretentivity. It is therefore desirable to assemble the rotor as abovedescribed, and to hold the pole pieces in place by the wedging meansheretofore referred to.

It will, of course, be understood that the present detailed descriptionof parts and the accompanying drawing relate to only a single preferredexecutional embodiment of the invention and that substantial changes maybe made in the described arrangement and construction of parts withoutdeparting from the spirit and full intended scope of the invention.

I claim:

l. A rotary magnet structure for magnetos of the rotating-field type,including a shaft of ferrous metal, a plurality of pole pieces disposedparallel to, and spaced about the shaft, an element bridging an endportion of a plurality of said pole pieces, pole shoes, a body ofnon-ferrous metal cast about the shaft between its ends and embracingthe bridging element and said pole shoes, and a locking member engagingthe opposite end portions of certain of the pole pieces. at pointswithin the body of cast metal.

2. A rotary magnet structure for magnetos of the rotating eld typeincluding a steel shaft, a plurality of pole pieces each having apreformed notched portion, said pole pieces being disposed parallel to,and spaced about the shaft, an element contacting, in bridging relation,end faces of certain of the pole pieces, laminated pole shoes eachhaving preformed pole-piece receiving openings, a body of non-magneticmetal cast onto an intermediate portion of the shaft, and embracing thebridging. element and said pole shoes, and a locking element engagingthe opposite end por-y tions of certain of-the pole pieces, within thebody of cast metal, and coacting therewith to maintain the pole piecesand bridging elements in contact with each other and to maintain thepole pieces in removable assembled relation in the structure.

3. A rotor structure for magnetos of the rotating field type including ashaft, a plurality of pole pieces having preformed notched portions,disposed in spaced relation about the shaft, and lengthwise thereof, abridging element en gaging a plurality of said pole pieces, pole shoes,a body of metal cast about an intermediate portion of the shaft, andembracing the bridging element and pole shoes, preformed sockets in saidcast body for receiving said pole pieces in assembly, a plurality ofwedge elements engaging the notched portions of certain ,of said polepieces, within the body of cast metal, and preformed channeled seats forthe wedge elements in said cast body.

4. A rotor structure for magnetos of the rotating field type includinga. shaft of ferrous metal, pole pieces disposed parallel to and spacedabout the shaft, pole-bridging elements each contacting with the endportions of a plurality of said pole pieces, pole shoes each consistingof a plurality of adjacent laminations disposed over certain of saidpole pieces, a body of non-magnetic metal die-cast about an intermediateportion of the shaft, and embracing the bridging elements, and poleshoes, tapered channels preformed within the body of cast metal, saidpole pieces having grooved portions, said body of cast metal and saidpole shoes having preformed pole-piece-receiving openings extendinglongitudinally of said shaft, locking pins of wedgesectiondisposedinsaid channels and each engaging grooved portions of aplurality of the pole pieces, within the cast metal body, when said polepieces are in magnetic contact with said bridging elements, the shaftbeing 'provided with a preformed roughened gripping surface on thatportion of the shaft within and engaged by the bodyof cast metal, andthe shaft projecting through such body, and beyond each opposite endthereof.

CURT F. REIS.

